1. Field of the Invention
The present invention relates to an ink composition that can be applied to the usage in ink jet recording, an image-forming method and a printed material for which the ink composition is used, and a new graft copolymer.
2. Description of the Related Art
As an image-recording method in which an image is formed on a recording medium such as paper on the basis of an image data signal, there are an electrophotographic method, a sublimation-type or melting-type thermal transfer method, an ink jet method, and the like.
In the electrophotographic method, there are problems in that a process for forming an electrostatic latent image on a photoreceptor drum through charging and exposure is required, the system becomes complicated, and consequently, the manufacturing cost becomes expensive. In addition, in the thermal transfer method, while the apparatus is not expensive, an ink ribbon is used, and thus there are problems of the expensive operation cost, the generation of waste materials, and the like.
On the other hand, in the ink jet method, since ink is discharged only to required image sections using an inexpensive apparatus, and an image is directly formed on a recording medium, ink can be efficiently used, there is an advantage of an inexpensive operation cost, furthermore, only a small amount of noise is generated, and the method is an excellent image-recording method.
Among ink compositions used to record images using the ink jet method, an active energy ray-curable aqueous ink composition has a number of excellent characteristics such that the ink composition can be preferably used for the printing of images, a pretreatment for imparting printing aptitude to recording media, a post treatment to protect and decorate printed images, and the like, the stability is excellent since the ink composition includes water as a major component, the ink composition can be applied to high-density ink jet recording by a decrease in the viscosity, and the like.
In recent years, ink images formed on a resin recording medium using an ink composition have been often provided for the usages of large-area advertisements, outdoor advertisements, and the like. Particularly, in the case of outdoor advertisements, strong water resistance is required. In addition, in a case in which a large-area printed material or a number of printed materials are continuously formed, a step for removing dirt in a printing apparatus using an organic solvent becomes necessary; however, in a case in which the organic solvent used for cleaning is scattered, and is attached to a formed ink image, when the image has poor solvent resistance, sections to which the solvent is attached are dissolved and removed, and image defects such as voids may be generated, and therefore there is a demand for an ink composition capable of forming an image having excellent water resistance and solvent resistance.
Examples of a basic constituent material of the active energy ray-curable aqueous ink composition include water, polymerizing substances, polymerization initiators initiating polymerization by generating a radical or the like by an active energy ray, and color materials (pigments and dyes). Among them, polymerizing substances and polymerization initiators can be prepared in an emulsion state, or can be present in a solution state by being imparted with water solubility by an appropriate substituent.
Examples of the active energy ray-curable aqueous ink composition in which the polymerizing substance and the polymerization initiator are water-soluble include the ink composition described in, for example, JP2005-307199A, and according to the ink composition, an ink composition for ink jet recording with which a film having excellent adhesiveness and the like can be obtained by light irradiation can be obtained.
In addition, JP2007-119449A and JP2000-160086A describe ink compositions including an active energy ray polymerizing substance having a specific maleimide structure.